1. Field of the Invention
The present invention relates to a method of forming an oxide superconducting thin film. More particularly, it relates to a method of forming a thin film of an oxide superconductor using laser ablation.
2. Description of the Background Art
While thin films are formed by various methods, laser ablation is regarded as a method which is suitable for forming a high-quality thin film since it requires absolutely no electromagnetic field.
Particularly in an excimer laser ablation method employing an excimer laser as a laser source for emitting a high-energy laser beam in a short wavelength region of about 200 nm, it is possible to form a thin film at a high speed under a low substrate temperature. Further, such an excimer laser ablation method is considered a technique suitable for forming a thin film of an oxide superconductor, which is a multi-element compound, due to the following advantages:
1) It is possible to obtain a thin film which has no displacement in composition from a target.
2) The film can be formed in a wide atmosphere pressure region of up to about 1 Torr.
3) The growth rate can be extremely increased.
4) It is a thermal non-equilibrium process with a high-energy beam.
However, the excimer laser is a pulse oscillation type laser, which has an extremely short emission time of about ten-odd nanoseconds in general. In a laser ablation method employing the aforementioned excimer laser as a light source, therefore, the target is intermittently irradiated with a pulsed laser beam.
In a laser ablation method, particles or vapor is generally scattered from a target only when the target is irradiated with a laser beam. Such particles or vapor scattered from the target is deposited on the surface of a substrate to form a thin film, due to reaction on the surface of the substrate. In the excimer laser ablation method, therefore, the particles or vapor is intermittently scattered from the target in response to laser pulses.
In the excimer laser having an extremely short pulse width and high energy, it is possible to generate a large quantity of particles or vapor with a laser beam of a single pulse. Thus, the as-formed film is remarkably influenced by the energy state of the laser.